It came as an unwelcome surprise to many Facebook friends and bored cubicle dwellers yesterday: Scrabulous was gone. The popular Scrabble knockoff was no longer available to U.S. users of the social networking site.

The free game had been one of the most popular applications on the social networking site, but a lawsuit filed last week accused Scrabulous of copyright infringement.

Hasbro and Mattel, the board game companies that share global ownership of the Scrabble trademark, had first asked Facebook to remove the application in January. Hasbro, which owns the rights in the United States and Canada, partnered with the game publisher Electronic Arts and recently introduced an authorized version of Scrabble for Facebook.

It's the latest example of the Web making something popular before copyright issues have been settled, reminiscent of YouTube's early skirmishes with television networks that complained about users posting copyrighted content.

According to its page on Facebook, Scrabulous had 509,505 daily users, and even Facebook founder Mark Zuckerberg has said he's a fan. The application was launched on Facebook last year by two brothers in India who are not affiliated with the social networking site.

Facebook users who logged on to play the word game instead got a notice that the application had been "disabled for US and Canadian users until further notice."

Some users noted on their pages at the site yesterday that they were going through "Scrabulous withdrawal."

John Edgell, a public relations consultant in the District, said he logged on to Facebook at 7:30 a.m. to continue a match yesterday, only to find that the application was down.

"I was getting creamed, so it's probably a good thing in that respect," he said. "The country is probably 10 percent more productive today."

Though the game is still available at Scrabulous.com, Arlington lawyer Peter Owen said he won't be playing it there because he primarily enjoyed taking on acquaintances he'd rediscovered on Facebook.

"Scrabble and Scrabulous are not really about the game. . . . What makes them fun is the way they help me connect with the personalities of my friends and family," he wrote in an e-mail. "The world is a sadder, lonelier place today. What kind of society are we that allows such a thing to happen?"

The two Facebook games use the same rules as the board game. EA's Scrabble has slicker animation, but some fans have complained that it runs more slowly than Scrabulous as a result.

Scrabulous fans didn't deny that the game was a knockoff of the venerable board game. Still, many were hoping Scrabble's owners would reach a deal with the Scrabulous creators.

"I'm surprised [Hasbro] let it stick around as long as they did," said Eric Litman, a Washington area tech entrepreneur who counts himself as a Scrabulous fan. "But I think they should've found a way to partner with these guys."

In a statement yesterday, Scrabulous co-creator Jayant Agarwalla said taking down the application in the United States and Canada was "an unfortunate event and not something that we are very pleased about."

EA introduced the test version of its Scrabble game for Facebook earlier this month; the final version is scheduled for an August release. In a statement yesterday, Hasbro tried to steer Scrabulous fans to the new application.

"In deference to the fans, we waited in pursuing legal action until Electronic Arts had a legitimate alternative available," the statement read. "We invite Scrabble fans in the U.S. and Canada to log onto Facebook and try out the authentic Scrabble application."

But the new Scrabble application generated many unfavorable comments yesterday at its Facebook page. EA said the application was the target of a malicious attack that disabled it for several hours yesterday. Users, meanwhile, complained that they couldn't get it to work.

"If you're going to shut down an application because of copyright infringement, make sure your own application works," complained one frustrated user.